Systems and methods for processing thin films

ABSTRACT

Methods and systems for processing a thin film are disclosed. Thin films are loaded onto two different loading fixtures, laser beam pulses are split into first and second laser beam pulses, the thin film loaded on one loading fixture is irradiated with the first laser beam pulses to induce crystallization while the thin film loaded on the other loading fixture is irradiated with the second laser beam pulses. At least a portion of the thin film loaded on the first and second loading fixtures is irradiated. The laser source system includes first and second laser sources and an integrator that combines the laser beam pulses to form combined laser beam pulses. The methods and system further utilize additional loading fixtures for processing additional thin film samples. The irradiation of additional thin film samples can be performed while thin film samples are being loaded onto the remaining loading fixtures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C §120 to U.S. patent application Ser. No. 12/101,648 filedon Apr. 11, 2008, and entitled “Systems and Methods for Processing ThinFilms,” which is division of and claims the benefit of priority under 35U.S.C §120 to U.S. patent application Ser. No. 10/754,133 filed on Jan.9, 2004, and entitled “Systems and Methods for Processing Thin Films,”which claims priority under 35 U.S.C. §119(e) to U.S. Provisional PatentApplication No. 60/503,346 filed on Sep. 16, 2003, and entitled “Systemsand Methods for Processing Thin Films,” both of which are herebyincorporated in their entirety by reference.

FIELD OF THE INVENTION

This invention relates to a method and system for processing thin films,and more particularly to forming crystalline thin films from amorphousor polycrystalline thin films using laser irradiation. In particular,the present disclosure relates to systems and methods that utilize laserbeam pulses to irradiate at least two thin films at the same time.

BACKGROUND OF THE INVENTION

In recent years, various techniques for crystallizing or improving thecrystallinity of an amorphous or polycrystalline semiconductor film havebeen investigated. This technology is used in the manufacture of avariety of devices, such as image sensors and active-matrixliquid-crystal display (AMLCD) devices. In the latter, a regular arrayof thin-film transistors (TFT) is fabricated on an appropriatetransparent substrate such that the TFTs serve as integration regionsand pixel regions.

Semiconductor films can be processed using excimer laser annealing(ELA), also known as line beam ELA, in which a region of the film isirradiated by an excimer laser to partially melt the film and thencrystallized. The process typically uses a long, narrow beam shape thatis continuously advanced over the substrate surface, so that the beamcan potentially irradiate the entire semiconductor thin film in a singlescan across the surface. ELA produces homogeneous small grainedpolycrystalline films; however, the method often suffers frommicrostructural non-uniformities which can be caused by pulse to pulseenergy density fluctuations and/or non-uniform beam intensity profiles.In addition, it may take approximately 200 second to 600 seconds tocompletely process the semiconductor film sample using the ELAtechniques, without even taking into consideration the time it takes toload and unload such sample.

Sequential lateral solidification (SLS) using an excimer laser is onemethod that has been used to form high quality polycrystalline filmshaving large and uniform grains. A large-grained polycrystalline filmcan exhibit enhanced switching characteristics because the reducednumber of grain boundaries in the direction of electron flow provideshigher electron mobility. SLS processing also provides controlled grainboundary location. U.S. Pat. Nos. 6,322,625 and 6,368,945 issued to Dr.James Im, and U.S. patent application Ser. Nos. 09/390,535 and09/390,537, the entire disclosures of which are incorporated herein byreference, and which are assigned to the common assignee of the presentapplication, describe such SLS systems and processes.

In an SLS process, an initially amorphous (or small grainpolycrystalline) silicon film is irradiated by a very narrow laserbeamlet, e.g., laser beam pulse. The beamlet is formed by passing alaser beam pulse through a slotted mask, which is projected onto thesurface of the silicon film. The beamlet melts the amorphous siliconand, upon cooling, the amorphous silicon film recrystallizes to form oneor more crystals. The crystals grow primarily inward from edges of theirradiated area toward the center. After an initial beamlet hascrystallized a portion of the amorphous silicon, a second beamlet isdirected at the silicon film at a location less than the lateral growthlength from the previous beamlet. Translating a small amount at a time,followed by irradiating the silicon film, promotes crystal grains togrow laterally from the crystal seeds of the polycrystalline siliconmaterial formed in the previous step. As a result of this lateralgrowth, the crystals produced tend to attain high quality along thedirection of the advancing beamlet. The elongated crystal grains areseparated by grain boundaries that run approximately parallel to thelong grain axes, which are generally perpendicular to the length of thenarrow beamlet. See FIG. 6 for an example of crystals grown according tothis method. One of the benefits of these SLS techniques is that thesemiconductor film sample and/or sections thereof can be processed(e.g., crystallized) much faster that it would take for the processingthe semiconductor film by the conventional ELA techniques. Typically,the processing/crystallization time of the semiconductor film sampledepends on the type of the substrates, as well as other factors. Forexample, it is possible to completely process/crystallize thesemiconductor film using the SLS techniques in approximately 50 to 100seconds not considering the loading and unloading times of such samples.

When polycrystalline material is used to fabricate electronic devices,the total resistance to carrier transport is affected by the combinationof barriers that a carrier has to cross as it travels under theinfluence of a given potential. Due to the additional number of grainboundaries that are crossed when the carrier travels in a directionperpendicular to the long grain axes of the polycrystalline material orwhen a carrier travels across a larger number of small grains, thecarrier will experience higher resistance as compared to the carriertraveling parallel to long grain axes. Therefore, the performance ofdevices fabricated on polycrystalline films formed using SLS, such asTFTs, will depend upon the crystalline quality and crystallineorientation of the TFT channel relative to the long grain axes, whichcorresponds to the main growth direction.

In order to uniformly process the semiconductor films, it is importantfor the beam pulse to be stable. Thus, to achieve the optimal stability,it is preferable to pulse or fire the beam constantly, i.e., withoutstopping the pulsing of the beam. Such stability may be reduced orcompromised when the pulsed beams are turned off or shut down, and thenrestarted. However, when the semiconductor sample is loaded and/orunloaded from a stage, the pulsed beam would be turned off, and thenturned back on when the semiconductor sample to be processed waspositioned at the designated location on the stage. The time for loadingand unloading is generally referred to as a “transfer time.” Thetransfer time for unloading the processed sample from the stage, andthen loading another to-be-processed sample on the stage is generallythe same for the ELA techniques and the SLS techniques. Such transfertime can be between 50 and 100 seconds.

In addition, the costs associated with processing semiconductor samplesare generally correlated with the number of pulses emitted by the beamsource. In this manner, a “price per shot/pulse” is established. If thebeam source is not shut down (i.e., still emit the beam pulses) when thenext semiconductor sample is loaded unto the stage, or unloaded from thestage, the number of such irradiations by the beam source when thesample is not being irradiated by the beam pulse and corresponding timetherefore is also taken into consideration for determining the price pershot. For example, when utilizing the SLS techniques, the time of theirradiation, solidification and crystallization of the semiconductorsample is relatively short as compared to the sample processing timeusing the ELA techniques. In such case, approximately half of the beampulses are not directed at the sample since such samples are beingeither loaded into the stage or unloaded from the stage. Therefore, thebeam pulses that are not impinging the samples are wasted.

Accordingly, it is preferable to reduce the price per shot, withoutstopping the emission of the beam pulses. It is also preferable to beable to process two or more semiconductor samples at the same time,without the need to stop or delay the emission of the laser beam pulsesgenerated by the laser source until the samples are loaded on therespective stages.

SUMMARY OF THE INVENTION

Laser systems are capable of generating laser beam pulses that havesufficient energy and pulse durations to process more than one thin filmsample at a time. To efficiently utilize the generated laser beam pulsesto process thin film samples, such laser beam pulses can be split intocomponent laser beam pulses. Thin film samples can then be irradiatedwith the component laser beam pulses. By generating and splitting laserbeam pulses that have sufficient energy and pulse durations to processmore than one thin film sample at a time, the energy generated by thelaser system can be more efficiently utilized in processing the thinfilm samples. By efficiently utilizing the energy that is produced bythe laser system, the manufacturing costs for producing thin films canbe reduced, e.g., the price per shot/pulse can be reduced.

The present invention is directed to systems and methods for inducingthe melting and subsequent crystallization (upon cooling) of thin films.Generated laser beam pulses can be split into two or more componentlaser beam pulse that can be used to simultaneously irradiate, viadifferent optical paths, a plurality of thin film samples or,alternatively, can be used simultaneously to irradiate different regionsof one thin film sample. An optical path, as that term is used herein,refers to the trajectory of a laser beam pulse as the laser beam pulsetravels from a laser beam source to a thin film sample. Optical pathsthus extend through both the illumination and projection portions of theexemplary systems. Each optical path has at least one optical elementthat is capable of manipulating the energy beam characteristics of alaser beam pulse that is directed along that optical path. Thus, byhaving optical paths that include different optical elements, laser beampulses having different energy beam characteristics can be directed viathe different optical paths to different regions of the thin film sampleor, alternatively, to different thin film samples

In one aspect of the invention, a method of processing a plurality ofthin films includes: loading a first thin film onto a first loadingfixture; loading a second thin film onto a second loading fixture;generating laser beam pulses each having a pulse duration; splitting thegenerated laser beam pulses into at least first laser beam pulses andsecond laser beam pulses, wherein the first laser beam pulses and thesecond laser beam pulses each have pulse durations which aresubstantially equal to the pulse duration of the generated laser beampulses; directing the first laser beam pulses onto a first optical pathand directing the second laser beam pulses onto a second optical path;irradiating the first thin film with the first laser beam pulses toinduce the melting and subsequent crystallization of at least a portionof the first thin film; and irradiating the second thin film with thesecond laser beam pulses to induce the melting and subsequentcrystallization of at least a portion of the second thin film.

In certain embodiments, at least a portion of the step of irradiatingthe first thin film and at least a portion of the step of irradiatingthe second thin film occur simultaneously.

In accordance with another aspect of the invention, the step ofgenerating the laser beam pulses includes: generating first componentlaser beam pulses each having a first pulse duration; generating secondcomponent laser beam pulses each having a second pulse duration; andcombining the first component laser beam pulses with the secondcomponent laser beam pulses to form the generated laser beam pulses.

In certain embodiment, the method further includes: loading a third thinfilm onto a third loading fixture while the first thin film is beingirradiated; irradiating the third thin film with the first laser beampulse to induce the melting and subsequent crystallization of at least aportion of the third thin film upon completing the processing of thefirst thin film; unloading the first thin film from the first loadingfixture; and loading another thin film onto the first loading fixture,wherein the steps of unloading the first thin film from the firstloading fixture and loading another thin film onto the first loadingfixture substantially occur while the third thin film is beingirradiated.

In certain other embodiments, the method further includes: loading afourth thin film onto a fourth loading fixture while the second thinfilm is being irradiated; irradiating the fourth thin film with thesecond laser beam pulses to induce the melting and subsequentcrystallization of at least a portion of the fourth thin film uponcompleting the processing of the second thin film; unloading the secondthin film from the second loading fixture; and loading another thin filmonto the second loading fixture, wherein the steps of unloading thesecond thin film from the second loading fixture and loading anotherthin film onto the second loading fixture substantially occur while thefourth thin film is being irradiated.

In accordance with another aspect of the invention, a method ofprocessing a thin film includes: loading a thin film onto a loadingfixture; generating a laser beam pulse having a pulse duration;splitting the generated laser beam pulses into at least a first laserbeam pulse and a second laser beam pulse, wherein the first laser beampulse and the second laser beam pulse have pulse durations which aresubstantially equal to the pulse duration of the generated laser beampulse; irradiating a first region of the thin film with the first laserbeam pulse to induce the melting and subsequent crystallization of thefirst region of the thin film; and irradiating a second region of thethin film with the second laser beam pulse to induce the melting andsubsequent crystallization of the second region of the thin film,wherein at least portions of the steps of irradiating the first regionand irradiating the second region occur simultaneously.

In one aspect of the invention, the methods of processing thin films canbe utilized to perform excimer laser anneal (ELA) processing, sequentiallateral solidification (SLS) processing or uniform grain structure (UGS)crystallization processing.

In one aspect of the invention, a system for processing a plurality ofthin films includes: a laser source system for generating laser beampulses each having a pulse duration; a first loading fixture forsecuring a thin film; a second loading fixture for securing a thin film;a beam splitting element for splitting the generated laser beam pulsesinto at least first laser beam pulses and second laser beam pulses,wherein the first laser beam pulses and second laser beam pulses eachhave pulse durations which are substantially equal to the pulse durationof the generated laser beam pulses; and wherein a thin film loaded onthe first loading fixture can be irradiated with the first laser beampulses and a thin film loaded on the second loading fixture can beirradiated with the second laser beam pulses.

In accordance with another aspect of the invention, the laser sourcesystem includes: a first laser source for generating first componentlaser beam pulses each having a first pulse duration; a second lasersource for generating second component laser beam pulses each having asecond pulse duration; and an integrator for combining the firstcomponent laser beam pulses with the second component laser beam pulsesto form the generated laser beam pulses.

In certain embodiments, the system further includes a third loadingfixture for securing a thin film wherein a thin film loaded on the thirdloading fixture can be irradiated with the first laser beam pulses. Abeam steering element can be utilized to direct the first laser beampulses to the first loading fixture and the third loading fixture.

In certain other embodiments, the system additionally includes a fourthloading fixture for securing a thin film wherein a thin film loaded onthe fourth loading fixture can be irradiated with the second laser beampulses.

In accordance with yet another aspect of the invention, a system forprocessing a thin film includes: a laser source system for generating alaser beam pulse having a pulse duration; a holding fixture for securinga thin film; a beam splitting element for splitting the generated laserbeam pulses into at least first laser beam pulses and second laser beampulses, wherein the first laser beam pulses and second laser beam pulseshave pulse durations which are substantially equal to the pulse durationof the generated laser beam pulses; and wherein a region of a thin filmthat is loaded on the holding fixture can be irradiated with the firstlaser beam pulses and a different region of the thin film loaded on theloading fixture can be simultaneously irradiated with the second laserbeam pulses.

According to one aspect of the invention, the laser source systemconsists of at least one continuous wave laser, solid-state laser orexcimer laser.

BRIEF DESCRIPTION OF THE DRAWING

Various objects, features, and advantages of the present invention canbe more fully appreciated with reference to the following detaileddescription of the invention when considered in connection with thefollowing drawing, in which like reference numerals identify likeelements. The following drawings are for the purpose of illustrationonly and are not intended to be limiting of the invention, the scope ofwhich is set forth in the claims that follow.

FIG. 1 illustrates the process of excimer laser annealing according toone or more embodiments of the present invention.

FIG. 2 shows a diagram of an exemplary system for performing asequential lateral solidification according to one or more embodimentsof the present invention.

FIG. 3 shows a mask for using in a sequential lateral solidificationaccording to one or more embodiments of the present invention

FIG. 4 illustrates a step in the process of sequential lateralsolidification according to one or more embodiments of the presentinvention.

FIG. 5 illustrates a step in the process of sequential lateralsolidification according to one or more embodiments of the presentinvention.

FIG. 6 illustrates a step in the process of sequential lateralsolidification according to one or more embodiments of the presentinvention.

FIG. 7A through FIG. 7C illustrate a sequential lateral solidificationprocess according to one or more embodiments of the present invention.

FIG. 8 is a prior art system for processing a thin film sample.

FIG. 9 is a flow chart of an exemplary embodiment of a process accordingto the present invention in which more than one thin film sample isirradiated at a time.

FIG. 10 depicts an exemplary system for processing a plurality of thinfilm sample in accordance with the present invention.

FIG. 11 depicts an exemplary laser source system for generating laserbeam pulses in accordance with the present invention.

FIG. 12A through FIG. 12C depict exemplary laser beam pulses generatedby the laser source system of FIG. 11.

FIG. 13 depicts another exemplary system for processing a plurality ofthin film sample in accordance with the present invention.

FIG. 14 depicts an exemplary system for processing a plurality of thinfilm sample in accordance with the present invention where thin filmsamples are loaded and unloaded onto a loading fixture while thin filmsamples are being processed on other loading fixtures.

FIG. 15 depicts an exemplary system for processing a plurality of thinfilm sample in accordance with the present invention where thin filmsamples are loaded and unloaded onto third and fourth loading fixtureswhile thin film samples are being processed on other loading fixtures.

DETAILED DESCRIPTION OF THE INVENTION

The quality of a film that has been crystallized using a laser-inducedcrystallization growth technique depends, in part, on the energy beamcharacteristics of the laser beam pulse that is used to irradiate thefilm and in the manner in which these laser beams are delivered, e.g.,continuous scan, two-shot, n-shot, to the film. This observation is usedto crystallize different regions of the films with laser beams havingdifferent energy beam characteristics in an energy- and time-efficientmanner and to provide the film performance characteristics needed indevice to be fabricated. Laser-induced crystallization is typicallyaccomplished by laser irradiation using a wavelength of energy that canbe absorbed by the film. The laser source may be any conventional lasersource, including but not limited to, excimer laser, continuous wavelaser and solid-state laser. The irradiation beam pulse can be generatedby another known source or short energy pulses suitable for melting asemiconductor can be used. Such known sources can be a pulsed solidstate laser, a chopped continuous wave laser, a pulsed electron beam anda pulsed ion beam, etc.

The systems and methods of the present disclosure can be utilized toprocess a wide variety of types of thin films. In certain embodiments,for example, the described systems and methods can be used to process(e.g., induce and achieve desired crystallization) semiconductor thinfilms. Such semiconductor thin films can be comprised of silicon,germanium or silicon germanium. Other semiconductor materials, however,may also be used to make up a semiconductor thin film. In certain otherembodiments, the described systems and methods may be used to processthin films that are comprised of a metallic material, such as aluminum,copper, nickel, titanium, gold and molybdenum, for example. In certainembodiments, an intermediate layer located beneath the thin film isutilized to protect the substrate from the heat and to preventimpurities from able to diffuse into the thin film. The intermediatelayer can be comprised of silicon oxide, silicon nitride and/or mixturesof oxide, nitride or a wide variety of other suitable materials.

Improvements in crystal properties are typically observed regardless ofthe specific crystallization process employed. The films can belaterally or transversely crystallized, or the films can crystallizeusing spontaneous nucleation. By “lateral crystal growth” or “lateralcrystallization,” as those terms are used herein, it is meant a growthtechnique in which a region of a film is melted to the film/surfaceinterface and in which recrystallization occurs in a crystallizationfront moving laterally across the substrate surface. By “transversecrystal growth” or “transverse crystallization,” as those terms are suedherein, it is meant a growth technique in which a region of film ispartially melted, e.g., not through its entire thickness, and in whichrecrystallization occurs in a crystallization front moving across thefilm thickness, e.g., in a direction transverse to that of theabove-described lateral crystallization. In spontaneous nucleation,crystal growth is statistically distributed over the melted regions andeach nucleus grows until it meets other growing crystals. Exemplarycrystallization techniques include excimer laser anneal (ELA),sequential lateral solidification (SLS), and uniform grain structure(UGS) crystallization.

Referring to FIG. 1, the ELA process uses a long and narrow shaped beam100 to irradiate the thin film. In ELA, a line-shaped and homogenizedexcimer laser beam pulses are generated and scanned across the filmsurface. For example, the width 124 of the center portion of the ELAbeam can be up to about 1 cm (typically about 0.4 mm) and the length 120can be up to about 70 cm (typically about 400 mm) so that the beam canpotentially irradiate the entire semiconductor thin film 126 in a singlepass. The excimer laser light is very efficiently absorbed in, forexample, an amorphous silicon surface layer without heating theunderlying substrate. With the appropriate laser pulse duration (approx.20-50 ns) and intensity (350-400 mJ/cm²), the amorphous silicon layer israpidly heated and melted; however, the energy dose is controlled sothat the film is not totally melted down to the substrate. As the meltcools, recrystallization into a polycrystalline structure occurs. Linebeam exposure is a multishot technique with an overlay of 90% to 99%between shots. The properties of silicon films are dependent upon thedose stability and homogeneity of the applied laser light. Line-beamexposure typically produces films with an electron mobility of 100 to150 cm²/V-s.

Referring to FIG. 2, an apparatus 200 is shown that may be used forsequential lateral solidification and/or for uniform grain structurecrystallization. Apparatus 200 has a laser source 270. Laser source 270may include a laser (not shown) along with optics, including mirrors andlens, which shape a laser beam pulse 272 (shown by dotted lines) anddirect it toward a substrate 274, which is supported by a stage 278. Thelaser beam pulse 272 passes through a mask 280 supported by a maskholder 282. The laser beam pulses 272 generated by the beam source 270provide a beam intensity in the range of 10 mJ/cm² to 1 J/cm², a pulseduration in the range of 20 to 300 nsec, and a pulse repetition rate inthe range of 10 Hz to 300 Hz. Currently available commercial lasers suchas Lambda STEEL 1000 available from Lambda Physik, Ft. Lauderdale, Fla.,can achieve this output. As the power of available lasers increases, theenergy of the laser beam pulses 272 will be able to be higher, and themask size will be able to increase as well. After passing through themask 280, the laser beam pulse 272 passes through projection optics 284(shown schematically). The projection optics 284 reduces the size of thelaser beam, and simultaneously increases the intensity of the opticalenergy striking the substrate 274 at a desired location 276. Thedemagnification is typically on the order of between 3× and 7×reduction, preferably a 5× reduction, in image size. For a 5× reductionthe image of the mask 280 striking the surface at the location 276 has25 times less total area than the mask, correspondingly increasing theenergy density of the laser beam pulse 272 at the location 276.

The stage 278 is a precision x-y stage that can accurately position thesubstrate 274 under the beam 272. The stage 278 can also be capable ofmotion along the z-axis, enabling it to move up and down to assist infocusing or defocusing the image of the mask 280 produced by the laserbeam pulses 272 at the location 276. In another embodiment of the methodof the present invention, it is preferable for the stage 278 to also beable to rotate.

In uniform grain structure (UGS) crystallization, a film of uniformcrystalline structure is obtained by masking a laser beam pulse so thatnon-uniform edge regions of the laser beam pulse do not irradiate thefilm. The mask can be relatively large, for example, it can be 1 cm×0.5cm; however, it should be smaller than the laser beam size, so that edgeirregularities in the laser beam are blocked. The laser beam pulseprovides sufficient energy to partially or completely melt theirradiated regions of the thin film. UGS crystallization provides asemiconductor film having an edge region and a central region of uniformfine-grained polycrystals of different sizes. In the case where thelaser irradiation energy is above the threshold for complete melting,the edge regions exhibit large, laterally grown crystals. In the casewhere the laser irradiation energy is below the threshold for completemelting, grain size will rapidly decrease from the edges of theirradiated region. For further detail, see U.S. application Ser. No.60/405,084, filed Aug. 19, 2002 and entitled “Process and System forLaser Crystallization Processing of Semiconductor Film Regions on aSubstrate to Minimize Edge Areas, and Structure of Such SemiconductorFilm Regions,” which is hereby incorporated by reference.

Sequential lateral solidification is a particularly useful lateralcrystallization technique because it is capable of grain boundarylocation-controlled crystallization and provides crystal grain ofexceptionally large size. Sequential lateral solidification produceslarge grained semiconductor, e.g., silicon, structures throughsmall-scale translations between sequential pulses emitted by an excimerlaser. The invention is described with specific reference to sequentiallateral solidification of an amorphous silicon film; however, it isunderstood that the benefits of present invention can be readilyobtained using other lateral crystallization techniques or other filmmaterials.

FIG. 3 shows a mask 310 having a plurality of slits 320 with slitspacing 340. The mask can be fabricated from a quartz substrate andincludes a metallic or dielectric coating that is etched by conventionaltechniques to form a mask having features of any shape or dimension. Thelength of the mask features is chosen to be commensurate with thedimensions of the device that is to be fabricated on the substratesurface. The width 360 of the mask features also may vary. In someembodiments it is chosen to be small enough to avoid small grainnucleation within the melt zone, yet large enough to maximize lateralcrystalline growth for each excimer pulse. By way of example only, themask feature can have a length of between about 25 and 1000 micrometers(μm) and a width of between about two and five micrometers (μm).

An amorphous silicon thin film sample is processed into a single orpolycrystalline silicon thin film by generating a plurality of excimerlaser pulses of a predetermined fluence, controllably modulating thefluence of the excimer laser pulses, homogenizing the modulated laserpulses, masking portions of the homogenized modulated laser pulses intopatterned beamlets, irradiating an amorphous silicon thin film samplewith the patterned beamlets to effect melting of portions thereofirradiated by the beamlets, and controllably translating the sample withrespect to the patterned beamlets (or vice versa) to thereby process theamorphous silicon thin film sample into a single or grainboundary-controlled polycrystalline silicon thin film.

In one or more embodiments of the sequential lateral solidificationprocess, highly elongated crystal grains that are separated by grainboundaries that run approximately parallel to the long grain axes areproduced. The method is illustrated with reference to FIG. 4 throughFIG. 6.

FIG. 4 shows the region 440 prior to crystallization. A laser pulse isdirected at the rectangular area 460 causing the amorphous silicon tomelt. Crystallization is initiated at solid boundaries of region 460 andcontinues inward towards centerline 480. The distance the crystal grows,which is also referred to as the lateral growth length, is a function ofthe amorphous silicon film thickness, the substrate temperature, theenergy beam characteristics, the buffer layer material, if any, the maskconfiguration, etc. A typical lateral growth length for 50 nm thickfilms is approximately 1.2 micrometers. After each pulse the image ofthe opening is advanced by an amount not greater than the lateral growthlength. In order to improve the quality of the resultant crystals, thesample is advanced much less than the lateral crystal growth length,e.g., not more than one-half the lateral crystal growth length. Asubsequent pulse is then directed at the new area. By advancing theimage of the slits 460 a small distance, the crystals produced bypreceding steps act as seed crystals for subsequent crystallization ofadjacent material. By repeating the process of advancing the image ofthe slits and firing short pulses the crystal grows in the direction ofthe slits' movement.

FIG. 5 shows the region 440 after several pulses. As is clearly shown,the area 500 that has already been treated has formed elongated crystalsthat have grown in a direction substantially perpendicular to the lengthof the slit. Substantially perpendicular means that a majority of linesformed by crystal boundaries 520 could be extended to intersect withdashed center line 480.

FIG. 6 shows the region 440 after several additional pulses followingFIG. 5. The crystals have continued to grow in the direction of theslits' movement to form a polycrystalline region. The slits preferablycontinue to advance at substantially equal distances. Each slit advancesuntil it reaches the edge of a polycrystalline region formed by the slitimmediately preceding it.

The sequential lateral solidification process can produce a film havinghighly elongated, low defect grains. In one or more embodiments, thisprocess is used to process those regions of the semiconductor thin filmthat are used for high performance devices. The polycrystalline grainsobtained using this process are typically of high mobility, e.g.,300-400 cm²/V-s. These highly elongated grains are well suited for theintegrated circuitry regions on an AMLCD device.

According to the above-described method of sequential lateralsolidification, the entire mask area is crystallized using multiplepulses. This method is hereinafter referred to as an “n-shot” process,alluding to the fact that a variable, or “n”, number of laser pulses(“shots”) are required for complete crystallization. Further detail ofthe n-shot process is found in U.S. Pat. No. 6,322,625, entitled“Crystallization Processing of Semiconductor Film Regions on a Substrateand Devices Made Therewith,” and in U.S. Pat. No. 6,368,945, entitled“System for Providing a Continuous Motion Sequential LateralSolidification,” both of which are incorporated in their entireties byreference.

In one or more embodiments, regions of the semiconductor film areprocessed using a sequential lateral solidification process thatproduces shorter crystal grains than those of the preceding “n-shot”method. The film regions are therefore of lower electron mobility;however the film is processed rapidly and with a minimum number ofpasses over the film substrate, thereby making it a cost-efficientprocessing technique. These crystallized regions are well suited for theregions of the semiconductor thin film that are used for making pixelcontrol devices of an AMLCD device.

The process uses a mask such as that shown in FIG. 3, where closelypacked mask slits 320 having a width 360, of about by way of example 4μm, are each spaced apart by spacing 340 of about, by way of example, 2μm. The sample is irradiated with a first laser pulse. As shown in FIG.7A, the laser pulse melts regions 710, 711, 712 on the sample, whereeach melt region is approximately 4 μm wide 720 and is spacedapproximately 2 μm apart 721. This first laser pulse induces crystalgrowth in the irradiated regions 710, 711, 712 starting from meltboundaries 730 and proceeding into the melt region, so thatpolycrystalline silicon 740 forms in the irradiated regions, as shown inFIG. 7B.

The sample is then translated approximately half the distance (orgreater) of the sum of the width 360 and spacing 340, and the film isirradiated with a second excimer laser pulse. The second irradiationmelts the remaining amorphous regions 742 spanning the recentlycrystallized region 740 and initial crystal seed region 745 to melt. Asshown in FIG. 7C, the crystal structure that forms the central section745 outwardly grows upon solidification of melted regions 742, so that auniform long grain polycrystalline silicon region is formed.

According to the above-described method of sequential lateralsolidification, the entire mask area is crystallized using only twolaser pulses. This method is hereinafter referred to as a “two-shot”process, alluding to the fact that only two laser pulses (“shots”) arerequired for complete crystallization. Further detail of the two-shotprocess is found in Published International Application No. WO 01/18854,entitled “Methods for Producing Uniform Large-Grained and Grain BoundaryLocation Manipulated Polycrystalline Thin Film Semiconductors UsingSequential Lateral Solidification,” which is incorporated in itsentirety by reference.

FIG. 8 illustrates a typical system 10 that can be used to induce themelting and subsequent crystallization of a thin film sample. Referringto FIG. 8, the system 10 includes a laser source 12, an attenuator 14which is utilized in conjunction with a pulse duration extender 16, atelescope 18, a homogenizer 20, a condenser lens 22, a mirror 24, avariable-focus field lens 26, a mask 28, mirrors 30 and 32, a projectionlens 34 and a handling stage 38 (i.e., a loading fixture). The lasersource 12 is capable of generating laser beam pulses 42 that have setpulse durations. The attenuator 14 can be a variable attenuator, e.g.,having a dynamic range of 10 to 1, capable of adjusting the energydensity of the generated laser beam pulses 42. Since crystal growth canbe a function of the duration of the pulse, a pulse duration extender 16is often used to lengthen the duration of each generated laser beampulse 42 to achieve a desired pulse duration. The telescope 18 can beused to efficiently adapt the beam profile of the laser beam pulse 42 tothe aperture of the homogenizer 20. The homogenizer 20 can consist oftwo pairs of lens arrays (two lens arrays for each beam axis) that arecapable of generating a laser beam pulses 42 that have uniform energydensity profiles. The condenser lens 22 can condense the laser beampulse 42 onto the variable-focus field lens 26. The mask 28 is typicallymounted to a mask stage (not shown) that is capable of accuratelypositioning the mask 28 (e.g., in three dimensions) in relationship tothe incoming laser beam pulse 42.

The energy beam characteristics of the laser beam pulses 42 generated bythe laser source 12 are modified by the optical elements of system 10 toproduce laser beam pulses 42 a that have desired energy beamcharacteristics, e.g., beam energy profile (density), beam shape, beamorientation, beam pulse duration, etc. As previously discussed, theamorphous silicon film 36 can be deposited in a controlled manner upon asurface of a substrate (not shown). The handling stage 38 is capable ofaccurately positioning the thin film 36 (e.g., in three dimensions) inrelation to the incoming laser beam pulses 42 a. The handling stage 38can operate in a continuous scanning mode or, alternatively, a steppermode. Laser beam pulses 42 a thus are directed to portions of the thinfilm sample to induce the melting and subsequent crystallization of thethin film sample, e.g., via two-shot or n-shot SLS processing.

As discussed above, to achieve a laser beam pulse 42 a that hasacceptable energy beam characteristics, many systems today utilize apulse duration extender 16 to extend the pulse duration of the laserbeam pulses 42 that are generated by the laser source 12. When using apulse duration extender, however, some of the energy of the generatedlaser beam pulse 42 will become lost during the “extension” processsince pulse duration extenders tend to be inefficient (e.g., theefficiencies of a pulse duration extender may range from between50-80%). This inability to utilize all of the energy which is generatedby the laser source can lead to increased processing times and, thus,lower manufacturing throughput. System 10 also suffers from thedisadvantage that only a single thin film sample can be processed (i.e.,irradiated) at a time.

Exemplary systems and processes according to the present invention canemploy principles and components thereof to process more than one thinfilm sample at a time. An exemplary process is set forth in the flowdiagram 900 of FIG. 9. Flow diagram 900 illustrates a method forsimultaneously irradiating two thin film samples that are located onseparate handling stages (i.e., loading fixtures) while other thin filmsamples are being unloaded from and loaded onto other handling stages.

In steps 910 a and 910 b, thin film samples (which may be mounted onsubstrates) are loaded onto a first loading fixture and a second loadingfixture, respectively. The deposition and/or fabrication of a thin filmon a substrate is well known in the art. In step 912 laser beam pulsesare generated. In step 914 the generated laser beam pulses are splitinto first laser beam pulses and second laser beam pulses. In certainpreferred embodiments, the first and second laser beam pulses have pulsedurations that are substantially the same. In step 916 a the first laserbeam pulses are directed to the first loading fixture and the thin filmsample loaded on the first loading fixture is irradiated with the firstlaser beam pulses to induce the melting and subsequent crystallizationof the thin film sample, step 918 a. In step 916 b the second laser beampulses are directed to the second loading fixture and the thin filmsample loaded on the second loading fixture is irradiated with thesecond laser beam pulses to induce the melting and subsequentcrystallization of the thin film sample, step 918 b. In an exemplaryembodiment, at least a portion of the thin film loaded on the firstloading fixture is also being irradiated (steps 916 a and 918 a) whileat least a portion of the thin film loaded on the second loading fixtureis also being irradiated (steps 916 b and 918 b). Thus, in this manner,more than one thin film sample can be processed simultaneously. Theprocessing of the thin film sample loaded on the first loading fixtureis continued until the processing is complete, step 920 a. Similarly,the processing of the thin film sample loaded on the second loadingfixture is also continued until the processing is complete, step 920 b.In certain embodiments, the (total) processing of the thin film sampleloaded on the first loading fixture coincides with the processing of thethin film sample loaded on the second loading fixture. In otherembodiments, however, the processing of the thin film sample loaded onthe first loading fixture does not coincide with the processing of thethin film sample loaded on the second loading fixture.

While the processing of the thin film samples loaded on the first andsecond loading fixtures is underway, other thin film samples are loadedonto a third loading fixture, step 922 a, and onto a fourth loadingfixture, step 922 b. Thus, while a thin film sample is being processed(i.e., irradiated), the unloading/loading of another thin film sampleonto an inactive (i.e., receiving no irradiation) loading fixture can beaccomplished. Upon completing the processing of the thin film samplewhich is loaded on the first loading fixture, the first laser beampulses are then directed to the third loading fixture, step 924 a,(where a thin film sample has already been loaded (step 922 a)) and theunloading of the processed thin film sample and the loading of a newthin film sample onto the first loading fixture, step 930 a, begins.Upon completing the processing of the thin film sample which is loadedon the second loading fixture, the second laser beam pulses are directedto the fourth loading fixture, step 924 b, (where a thin film sample hasalready been loaded (step 922 b)) and the unloading of the processedthin film sample and the loading of a new thin film sample onto thesecond loading fixture, step 930 b, begins.

In step 926 a the thin film sample loaded on the third loading fixtureis then irradiated with the first laser beam pulses to induce themelting and subsequent crystallization of the loaded thin film sample.In step 926 b the thin film sample loaded on the fourth loading fixtureis then irradiated with the second laser beam pulses to induce themelting and subsequent crystallization of this thin film sample. Theprocessing of the thin film samples loaded on the third and fourthloading fixtures is then continued until the processing is complete,steps 928 a and 928 b, respectively. Preferably, a new thin film sampleis already loaded onto the first loading fixture, step 930 a, before theprocessing of the thin film sample loaded on the third loading fixtureis completed. And, preferably, a new thin film sample is already loadedonto the second loading fixture, step 930 b, before the processing ofthe thin film sample loaded on the fourth loading fixture is completed.This method of unloading/loading thin film samples from/onto inactiveloading fixtures, while other thin film samples are being processed onactive loading fixtures, is continued until all the thin film sampleshave been processed, step 940. Flow diagram 900 thus provides a methodfor optimally using the power provided by the laser source and formaximizing the manufacturing throughput of the thin film processing.This is accomplished by maximizing the laser (irradiation) source's dutycycle, e.g., the laser source can remain on and its generated energy iscontinuously being utilized to facilitate the processing of thin filmsamples, and minimizing any downtime that may be necessary for theloading and unloading of the thin film samples onto and from the loadingfixtures.

An exemplary embodiment of a system constructed in accordance with thepresent invention is depicted in FIG. 10. System 1000 of FIG. 10includes a laser source system 50, a beam splitting element 70 and twoloading fixtures 122, 142. Thin film samples 118, 138 are loaded ontoloading fixtures 122 and 142, respectively. System 1000 may furtherinclude an automatic handling system(s) (not shown) that is capable ofloading the thin film samples onto the loading fixtures, so that thethin film samples may be processed, and removing the thin film samplesfrom the loading fixtures when processing has been completed. The lasersource system 50 is capable of generating laser beam pulses 52 that havesufficient energy to process (upon splitting) at least two thin filmsamples at the same time. Moreover, in most preferred embodiments, thelaser source system 50 is capable of generating laser beam pulses 52which have pulse durations that are sufficient to induce the desiredcrystallization processing of the thin film samples. Thus, in mostpreferred embodiments, a pulse duration extender does not need to beutilized to extend the pulse duration of the laser beam pulses 52generated by the laser source system 50.

System 1000 further includes a variable-focus field lens 112, a mask114, a projection lens 116, a mirror 144, a second variable-focus fieldlens 132, a second mask 134 and a second projection lens 136.Variable-focus field lens 112, mask 114 and projection lens 116 aredisposed between the beam splitting element 70 and the loading fixture122, while variable-focus field lens 132, mask 134 and projection lens136 are disposed between the beam splitting element 70 and the loadingfixture 142. In other embodiments, system 1000 may include different (orfewer) optical elements. Moreover, different optical elements may bepresent within the different optical paths that are located downstreamof the beam splitting element 70. Accordingly, the energy beamcharacteristics of the laser beam pulses that are used to irradiate thethin film samples can be tailored to meet the processing requirements ofthe thin samples that are to be processed. System 1000 further includesan attenuator 14, a telescope 18, a homogenizer 20 and a condenser lens22, which are located between the laser source system 50 and the beamsplitting element 70.

After traveling through the attenuator 14, telescope 18, homogenizer 20and condenser lens 22 (where the energy beam characteristics of thelaser beam pulses 52 are accordingly modified), laser beam pulses 52 arethen split by the beam splitting element 70 into first laser beam pulses58 and second laser beam pulses 56 which are directed to the firstloading fixture 122 and the second loading fixture 142, respectively.The beam splitting element 70 “splits” the laser beam pulses 52 bydistributing the energy density of the laser beam pulses 52 intoseparate component laser beam pulses 56 and 58. The component laser beampulses 56 and 58 produced by the beam splitting element 70 generallywill have the same pulse durations as the laser beam pulses 52 which aregenerated by the laser source system 50. Component laser beam pulses 56and 58, however, need not have the same energy densities. For example,in some embodiments, 60% of the energy density of the laser beam pulses52 may be used to form the first laser beam pulses 58 while, in otherembodiments, the energy densities of the component laser beam pulses 56and 58 may be substantially the same. While the beam splitting element70 of system 1000, as shown, only generates two component laser beampulses, in other embodiments the beam splitting element 70 is capable ofproducing several (e.g., three, four, etc.) component laser beam pulsesfrom the laser beam pulses 52 that are generated by the laser sourcesystem 50.

First laser beam pulses 58 travel through variable-focus lens 112, mask114 and projection lens 116 to form first laser beam pulses 58 a (e.g.,the energy beam characteristics of laser beam pulses 58 a will bedifferent than that of laser beam pulses 58). Thin film 118, which isloaded on loading fixture 122, is then irradiated with the laser beampulses 58 a. The loading fixture 122 is capable of accuratelypositioning the thin film 118 (e.g., in three dimensions) in relation tothe incoming first laser beam pulses 58 a. The loading fixture 122 canoperate in a continuous scanning mode or, alternatively, a stepper mode.Laser beam pulses 58 a thus are directed to portions of thin film 118 toinduce the melting and subsequent crystallization of the thin film 118,e.g., via two-shot or n-shot SLS processing. Upon completing theprocessing of the thin film 118 loaded on loading fixture 122, the thinfilm 118 is then removed from loading fixture 122 and another thin filmsample is substituted in its place.

Second laser beam pulses 56 similarly travel through variable-focus lens132, mask 134 and projection lens 136 to form second laser beam pulses56 a (e.g., the energy beam characteristics of laser beam pulses 56 awill be different than that of laser beam pulses 56). Thin film 138,which is loaded on loading fixture 142, is then irradiated with thelaser beam pulses 56 a. The loading fixture 142 is capable of accuratelypositioning the thin film 138 (e.g., in three dimensions) in relation tothe incoming second laser beam pulses 56 a. Loading fixture 142 canoperate in a continuous scanning mode or, alternatively, a stepper mode.Laser beam pulses 56 a thus are directed to portions of thin film 138 toinduce the melting and subsequent crystallization of the thin film 138,e.g., via two-shot or n-shot SLS processing. Upon completing theprocessing of the thin film 138 loaded on loading fixture 142—which neednot coincide with the processing of the thin film 118 that is loaded onloading fixture 122—thin film 138 can be removed from the loadingfixture 142 and another can be substituted in its place. The operationsof the laser source system 50, the beam steering element 70, and thehandling stages 122, 142, along with the systems (e.g., actuators,conveyors, etc) necessary for loading and unloading the thin filmsamples onto and from the loading fixtures 122, 142, and the otheroptical elements (if present) can be controlled by a programmablecomputer system (not shown). FIG. 10 thus illustrates a system forprocessing thin film samples where two thin film samples can beprocessed at the same time.

In an alternate embodiment, system 1000 can be configured so as tosimultaneously irradiate different portions of a single thin film sample(loaded on a loading fixture). In other words, in certain embodiments,system 1000 may only include a single loading fixture and laser beampulses 56 a and 58 a can be directed to different regions of the thinfilm that is loaded on the loading fixture. Thus, simultaneousprocessing of different regions of a thin film sample can beaccomplished in accordance with the teachings of the present invention.

As previously discussed, laser source system 50 is preferably capable ofgenerating laser beam pulses 52 that have sufficient energy to process(upon splitting) more than one thin film samples at a time. In mostexemplary embodiments, the laser source system 50 has a highpulse-to-pulse stability, e.g., less than 3% and preferable less than1.5%. Moreover, in most preferred embodiments, the laser source system50 is capable of generating laser beam pulses 52 which have pulsedurations that are sufficient to induce the desired crystallizationprocessing of the thin film samples. Thus, in certain preferredembodiments, a pulse duration extender does not need to be utilized toextend the pulse duration of the laser beam pulses 52 generated by thelaser source system 50. Appropriate laser source systems that arecapable of producing laser beam pulses 52 which have sufficient energyto process more than one thin film sample at a time are commerciallyavailable. For example, in certain embodiments, the laser source system50 of the present invention can be a high-pulse-energy excimer laser,such as the Lambda STEEL systems that are available from Lambda Physikor the SOPRA VEL 1510 that is available from SOPRA S.A.

In other exemplary embodiments, the laser source system 50 includes twoor more laser sources that generate component laser beam pulses that areintegrated together to form the laser beam pulses 52. FIG. 11illustrates one exemplary embodiment of a laser source system 50 thatutilizes two or more laser sources. FIGS. 12A-C illustrate various waysin which the component laser beam pulses of the laser source system 50of FIG. 11 can be integrated to form laser beam pulses 52. The lasersource system 50 of FIG. 11 includes a first laser source 60 a, a secondlaser source 60 b, mirrors 63 and an integrator 66. Referring to FIGS.11 and 12A, the first laser source 60 a generates component laser beampulses 62 a that have an energy profile, pulse cycle and pulse duration64 a as shown. The second laser source 60 b generates component laserbeam pulses 62 b that have an energy profile, pulse cycle and pulseduration 64 b as shown. In certain preferred embodiments, the energyprofiles, pulse cycles and pulse durations 64 a, 64 b of the componentlaser sources 60 a, 60 b are substantially similar, while in otherembodiments, the energy profiles, pulse cycles and/or pulse durationsare different. The laser beam pulses 62 a, 62 b are directed to theintegrator 66 via mirrors 63. The integrator 66 combines laser beampulses 62 a, 62 b together to form laser beam pulses 52 having aneffective pulse duration as shown in FIGS. 12A-C. The integrator 66 caninclude reflective elements that direct the laser beam pulses 62 a, 62 bonto the same optical path. As seen in FIGS. 12A-C, each component laserbeam pulse 62 a (having a pulse duration 64 a) is integrated (i.e.,paired) with a corresponding component laser beam pulse 62 b (having apulse duration 64 b) to effectively form a laser beam pulse 52. Thecomponent laser beam pulses 62 a, 62 b can be integrated together sothat (1) there is a small time delay between a laser beam pulse 62 a anda corresponding laser beam pulse 62 b, (2) a portion of a laser beampulse 62 a overlies a portion of a corresponding laser beam pulse 62 bso that the laser beam pulse 62 a, 62 b are constructively added wherethey overlie each other, or (3) a laser beam pulse 62 a completelyoverlies a corresponding laser beam pulse 62 b (and, thus, laser beampulse 62 a, 62 b constructively add to each other). The integration ofthe component laser beam pulses 62 a, 62 b (to form a laser beam pulse52) can be controlled, for example, by varying the timing of thegeneration of the component laser beam pulses 62 a, 62 b (with respectto each other), the pulse cycle at which the component laser beam pulses62 a, 62 b are being generated, the length of the pulse durations 64 a,64 b of the component laser beam pulses 62 a, 62 b, the path lengthsfound between the laser sources 60 a, 60 b and the integrator 60, theoperations of the integrator 60 (e.g., delayed biases, if present), orthe energy densities of the component laser beam pulses 62 a, 62 b.

As shown in FIG. 12A, in certain exemplary embodiments, a time delay dis inter-disposed between corresponding component laser beam pulses 62a, 62 b. In one preferred embodiment, the laser sources 60 a, 60 b aresynchronized to produce laser beam pulses 62 a, 62 b at substantiallyidentical frequencies (e.g., 300 hz) with a timed separation delay (e.g.50-500 nanoseconds) occurring between the generation of a laser beampulse 62 a and a corresponding laser beam pulse 62 b. In other words,laser source 60 a generates a first laser beam pulse 62 a while lasersource 60 b generates a first laser beam pulse 62 b shortly thereafter.The integrator 66 then combines the first laser beam pulse 62 a with thefirst laser beam pulse 62 b to form a first laser beam pulse 52, asshown in FIG. 12A. In the embodiment depicted in FIG. 12A, the resultingpulse duration of a generated laser beam pulse 52 is thus the sum of thepulse durations 64 a, 64 b (corresponding to laser beam pulses 62 a, 62b, respectively) and the time delay d. Laser sources 60 a, 60 b thencontinue to generate additional laser beam pulses 62 a, 62 b,respectively, and the integrator 66 combines the corresponding laserbeam pulses 62 a, 62 b together to form the laser beam pulses 52.

FIG. 12B shows an embodiment where a component laser beam pulse 62 bpartially overlaps a corresponding laser beam pulse 62 b to form anintegrated laser beam pulse 52, while FIG. 12C shows an embodiment wherea component laser beam pulse 62 b completely overlaps a correspondinglaser beam pulse 62 b to form an integrated laser beam pulse 52. In thearea where the component laser beam pulses 62 a, 62 b are constructivelyadded (i.e., where they overlap), the resulting energy profile of thelaser beam pulse 52 is indicated with a dashed line. In the embodimentdepicted in FIG. 12B, since the component laser beams pulse 62 a onlypartially overlap with the corresponding component laser beam pulses 62b, the resulting pulse durations of the integrated laser beam pulses 52will be less than the sum of the pulse durations 64 a, 64 b(corresponding to laser beam pulses 62 a, 62 b, respectively). In theembodiment depicted in FIG. 12C, the resulting pulse durations of theintegrated laser beam pulses 52 will be equal to the longer of the twopulse durations 64 a, 64 b (corresponding to laser beam pulses 62 a, 62b, respectively) since the component laser beams pulse 62 a fullyoverlap with the corresponding component laser beam pulses 62 b.

FIG. 13 depicts another exemplary embodiment of a system constructed inaccordance with the present invention. System 1100 of FIG. 13 is similarto system 1000 of FIG. 10 except that the optical elements (e.g.,attenuators, telescopes, homogenizers, condenser lenses, etc.) have beenmoved downstream of the beam splitting element 70. Thin films 230 and260 are loaded onto loading fixtures 232 and 262, respectively. Mirrors212, 222, attenuator 214, telescope 216, homogenizer 218, condenser lens220, variable-focus field lens 224, mask 226, and projection lens 228are disposed (along an optical path) between the beam splitting element70 and the loading fixture 232. Attenuator 244, telescope 246,homogenizer 248, condenser lens 250, mirror 252, variable-focus fieldlens 254, mask 256, and projection lens 258 are similarly disposed(along a different optical path) between the beam splitting element 70and the loading fixture 262. The laser source system 50 is capable ofgenerating laser beam pulses 52 that have sufficient energy to process(upon splitting) at least two thin film samples at the same time.Moreover, the laser source system 50 is capable of generating laser beampulses 52 which have pulse durations that are sufficient to induce thedesired crystallization processing of the thin film samples.

Laser beam pulses 52 are split by the beam splitting element 70 intofirst laser beam pulses 58 and second laser beam pulses 56 which aredirected to the first loading fixture 232 (and thin film 230 which isdisposed thereon) and the second loading fixture 262 (and thin film 260which is disposed thereon), respectively. First laser beam pulses 58travel through attenuator 214, telescope 216, homogenizer 218, condenserlens 220, variable-focus field lens 224, mask 226, and projection lens228 to form first laser beam pulses 58 a (e.g., the energy beamcharacteristics of laser beam pulses 58 a will tend to be different thanthat of laser beam pulses 58). The thin film 230 that is loaded onloading fixture 232 is then irradiated by the laser beam pulses 58 a.Upon completing the processing of thin film 230, the thin film 230 canbe removed from the loading fixture 232 and another can be substitutedin its place. Second laser beam pulses 56 similarly travel throughattenuator 244, telescope 246, homogenizer 248, condenser lens 250,variable-focus field lens 254, mask 256, and projection lens 258 to formsecond laser beam pulses 56 a (e.g., the energy beam characteristics oflaser beam pulses 56 a will tend to be different than that of laser beampulses 56). The thin film 260 that is loaded on loading fixture 262 isthen irradiated by the laser beam pulses 56 a. The loading fixtures 232,262 (and thus the corresponding thin films 230, 262) may be locatedwithin the same irradiation chamber or separate irradiation chambersdepending, for example, upon the operational conditions (e.g., pressure,temperature, etc.) that are to be maintained at the different loadingfixtures 232 and 262. Upon completing the processing of thin film260—which need not coincide with the processing of the thin film 230—thethin film 260 can be removed from the loading fixture 262 and anothercan be substituted in its place. System 1100 provides additionalflexibility in controlling the energy beam characteristics of the laserbeam pulses 58 a and 56 a to match the irradiation processingrequirements of the thin film samples that are being irradiated onloading fixtures 232 and 262, respectively. In other words, by placingmore of the optical elements downstream of the beam splitting element70, the energy beam characteristics of the laser beam pulses 56 a, 58 acan be more easily tailored to meet the (e.g., different) operationalrequirements of the thin film samples that are being processed.

FIG. 14 depicts yet another exemplary embodiment of a system constructedin accordance with the present invention. System 1200 of FIG. 14 isdifferent from the systems of FIGS. 10 and 13 in that it includes athird loading fixture. Preferably, at any given moment, two of theloading fixtures are being utilized for processing (i.e., irradiating)thin film samples while other thin film samples are being unloaded andloaded onto the third loading fixture. System 1200 includes a lasersource system 50, an attenuator 14, a telescope 18, a homogenizer 20, acondenser lens 22, a beam splitting element 70 and three loadingfixtures, fixtures 232, 262 and 372. Other optical elements (not shown),e.g., masks, projection lens, etc, as previously discussed, can bedisposed between the beam splitting element 70 and the respectiveloading fixtures 232, 262, and 372. The laser beam pulses 52 that aregenerated by the laser source system 50 enter the beam splitting element70 after passing through the optical elements as shown. Beam splittingelement 70 splits the laser beam pulses 52 into first laser beam pulses58 and second laser beam pulses 56 as previously discussed. However, inaddition to splitting laser beam pulses 52, beam splitting element 70 ofsystem 1200 is also capable of directing the spilt laser beam pulses 56,58 along the different optical paths which lead to the thin film samplesthat are loaded on the loading fixtures 232, 262, and 372. Since thebeam splitter element 70 of system 1200 only produces two componentlaser beam pulses 56, 58 and there are three loading fixtures, at anygiven moment at least one of the loading fixtures 232, 262, 372 is notreceiving a component laser beam pulse 56 or 58.

While a particular loading fixture is not receiving a component laserbeam pulse 56 or 58, a previously processed thin film sample can beunloaded from this loading fixture and an unprocessed thin film samplecan then be loaded. Once a thin film sample has been loaded onto thisloading fixture and the irradiation processing of a thin film samplethat is loaded on a different loading fixture has been completed, thecomponent laser beam pulses previously directed to the other loadingfixture can then be directed, via the beam splitting element 70, to thenow loaded thin film sample. For example, as shown in FIG. 14, firstlaser beam pulses 58 are initially directed to loading fixture 262(having thin film 260 disposed thereon) and second laser beam pulses 56are initially directed to loading fixture 232 (having thin film 230disposed thereon). While thin films 230 and 260 are being irradiated onloading fixtures 232 and 262, respectively, a thin film can be unloaded(if a processed thin film is present) and new thin film 370 can beloaded onto the inactive loading fixture 372. The processing of the thinfilms 230, 260 loaded on loading fixtures 232, 262 can be performedconcurrently or, alternatively, the processing of thin film 230 loadedon loading fixture 232 may be independent of the processing of thin film260 loaded on loading fixture 262, e.g., the processing times may be thesame or different, and if the same the processing sequences may bestaggered from each other, etc. Upon completing the irradiationprocessing of thin film 230, the beam splitter element 70 can thendirect the second laser beam pulses 56 to loading fixture 372 (havingthin film 370 disposed thereon), as shown by the dotted lines in FIG.14. The processed thin film 230 can then be removed from the loadingfixture 232 and a new unprocessed thin film sample can be loaded andreadied (on loading fixture 232) for processing.

FIG. 15 depicts a further exemplary embodiment of a system constructedin accordance with the present invention. System 1300 of FIG. 15includes four loading fixtures, fixtures 232, 262, 372, and 382.Preferably, at any given moment, two of the loading fixtures are beingutilized to process thin film samples while other thin film samples arebeing unloaded and loaded onto the two remaining loading fixtures.System 1300 includes a laser source system 50, an attenuator 14, atelescope 18, a homogenizer 20, a condenser lens 22, a beam splittingelement 70 and four loading fixtures, fixtures 232, 262, 372, and 382.Other optical elements (not shown), e.g., masks, projection lens, etc,as previously discussed, can be utilized downstream of the beamsplitting element 70 between the loading fixtures 232, 262, 372, and 382and the beam splitting element 70. Laser beam pulses 52 generated by thelaser source system 50 enter the beam splitting element 70 after passingthrough the optical elements as shown. Beam splitting element 70 splitsthe laser beam pulses 52 into first laser beam pulses 58 and secondlaser beam pulses 56 as previously discussed. However, unlike system1200, system 1300 also includes beam steering elements 80 a and 80 b.Beam steering elements 80 a, 80 b can act as switches for directing thesecond laser beam pulses 56 and first laser beam pulses 58,respectively. Such beam steering elements are readily known in the art.So, unlike the beam splitting element 70 of system 1200, which wascapable of both splitting laser beam pulse 52 and directing thecomponent laser beam pulses 56, 58 along a plurality of optical paths,system 1300 provides beam steering elements 80 a and 80 b that areseparate from the beam splitting element 70.

The first laser beam pulses 58 are directed from the beam splittingelement 70 to beam steering elements 80 b. Beam steering elements 80 bcontrols whether first laser beam pulses 58 are to be delivered toloading fixture 262 or, alternatively, to loading fixture 382. Thesecond laser beam pulses 56 are directed from the beam splitting element70 to beam steering elements 80 a. Beam steering elements 80 a controlswhether second laser beam pulses 56 are to be delivered to loadingfixture 232 or, alternatively, to loading fixture 372. Since the beamsplitter element 70 of system 1300 only “produces” two component laserbeam pulses 56, 58 and there are four loading fixtures (each of whichmay hold a thin film sample), at any given moment at least two of theloading fixtures 232, 262, 372, 382 are thus not receiving a componentlaser beam pulse 56, 58. Based upon the arrangement of system 1300, atany given moment, one of the loading fixtures 232 or 372 and one of theloading fixtures 262 or 382 are preferably receiving first laser beampulses 58 and second laser beam pulses 56, respectively. Moreover, whileone of the loading fixtures 232, 372 is receiving first laser beampulses 58, thin film samples can be unloaded/loaded onto the otherloading fixture. Similarly, while one of the loading fixtures 262, 382is receiving second laser beam pulses 56, thin film samples can beunloaded/loaded on the other load fixture.

For example, as shown in FIG. 15, first laser beam pulses 58 areinitially directed via beam steering element 80 b to loading fixture 262(having thin film 260 disposed thereon) and second laser beam pulses 56are initially directed via beam steering element 80 a to loading fixture232 (having thin film 230 disposed thereon). While thin films 230, 260of loading fixtures 232, 262, respectively, are being irradiated, thinfilm samples can be unloaded (if a processed thin film sample ispresent) and thin films 370, 380 can be loaded onto inactive loadingfixtures 372, 382, respectively. The processing of thin films 230, 260loaded on loading fixtures 232, 262 can be performed concurrently or,alternatively, the processing of thin film 230 loaded on loading fixture232 may be independent of the processing of thin film 260 that is loadedon loading fixture 262, e.g., the processing times may be the same ordifferent, and if the same the processing sequences may be staggeredfrom each other, etc. Upon completing the irradiation processing of thinfilm 230 (loaded on loading fixture 232), the beam steering element 80 athen directs the second laser beam pulses 56 to loading fixture 372, asshown by the dotted lines in FIG. 15, where thin film 370 has alreadybeen loaded. The processed thin film 230 can then be removed fromloading fixture 232 and a new unprocessed thin film sample can be loadedon loading fixture 230 and readied for processing. Similarly, uponcompleting the irradiation processing of thin film 260 (loaded onleading fixture 262), the beam steering element 80 b then directs thefirst laser beam pulses 58 to loading fixture 382, as shown by thedotted lines in FIG. 15, where thin film 380 has already been loaded.The processed thin film 260 can then be removed from loading fixture 262and a new unprocessed thin film sample can be loaded on loading fixture260 and readied for processing.

The methods of irradiating thin film samples loaded on a plurality ofloading fixtures while unloading/loading thin film samples on the otherloading fixtures which are not currently receiving irradiation cancontinue until the processing of all the thin film samples is completed.Thus the manufacturing throughput of systems 1200 and 1300 are furtherincreased (e.g., over systems 1000 and 1100) because at least a portionof the sample handling times of loading thin film samples onto and fromthe loading fixtures are done in parallel with the irradiationprocessing of other thin film samples. Depending upon the time it takesto unload and load thin film samples onto a loading fixture and theamount of time that is required to process a thin film sample, incertain embodiments the handling processing times can be completelyabsorbed within the irradiation processing times so that the handlingtimes do not contribute to the total manufacturing processing time.Accordingly, in certain embodiments, laser beam pulses that aregenerated by a laser source system that is constantly “on” can be fullyutilized in the processing of thin film samples.

Further detail is provided in co-pending provisional patent applicationentitled “Laser-Irradiated Thin Films Having Variable Thickness” filedconcurrently with the present disclosure, and in co-pending provisionalpatent application entitled “Systems And Methods For InducingCrystallization of Thin Films Using Multiple Optical Paths” filedconcurrently with the present disclosure, the contents of which areincorporated by reference.

The semiconductor device fabricated by the present invention includesnot only an element such as a TFT or a MOS transistor, but also a liquidcrystal display device (TFT-LCDs), an EL (Electro Luminescence) displaydevice, an EC (Electro Chromic) display device, active-matrix organiclight emitting diodes (OLEDs), static random access memory (SRAM),three-dimensional integrated circuits (3-D ICs), sensors, printers, andlight valves, or the like, each including a semiconductor circuit(microprocessor, signal processing circuit, high frequency circuit,etc.) constituted by insulated gate transistors.

Although various embodiments that incorporate the teachings of thepresent invention have been shown and described in detail herein, thoseskilled in the art can readily devise many other varied embodiments thatincorporate these teachings.

1. A system for processing a plurality of thin films, comprising: alaser source system for generating laser beam pulses each having a pulseduration; a first loading fixture for securing a thin film; a secondloading fixture for securing a thin film; a beam splitting element forsplitting said generated laser beam pulses into at least first laserbeam pulses and second laser beam pulses; and wherein a thin film loadedon said first loading fixture can be irradiated with said first laserbeam pulses and a thin film loaded on said second loading fixture can beirradiated with said second laser beam pulses, and wherein at least aportion of said thin film loaded on said second loading fixture can beirradiated while said thin film loaded on said first loading fixture isbeing irradiated.